remove serializer dependency from fieldset

test/serializers/fieldset_test.rb

@@ -0,0 +1,26 @@
+require 'test_helper'
+
+module ActiveModel
+  class Serializer
+    class FieldsetTest < Minitest::Test
+
+      def test_fieldset_with_hash
+        fieldset = ActiveModel::Serializer::Fieldset.new({'post' => ['id', 'title'], 'coment' => ['body']})
+
+        assert_equal(
+          {:post=>[:id, :title], :coment=>[:body]}, 
+          fieldset.fields
+        )
+      end
+
+      def test_fieldset_with_array_of_fields_and_root_name
+        fieldset = ActiveModel::Serializer::Fieldset.new(['title'], 'post')
+
+        assert_equal(
+          {:post => [:title]}, 
+          fieldset.fields
+        )
+      end
+    end
+  end
+end